Stator and rotor lamination construction for a dynamo-electric machine

ABSTRACT

A dynamo-electric machine includes a stator core fixed in a casing and formed of stator lamination plates, and a rotor supported in a bore of the stator core and formed of a stack of rotor lamination plates. Each stator lamination plate has a tooth portion extending radially outward from the bore to an intermediate circumference, and a yoke portion defined between the intermediate circumference and the outer periphery of the stator lamination plate. Each of the rotor lamination plates has a number of equally circumferentially spaced closed slots, wherein each slot is defined by a curvilinear edge at an upper slot region adjacent the periphery of the plate. The curvilinear edge together with a pair of spaced parallel sides together define a top part of each slot, the top part opening into a bottom part of the slot which is substantially triangularly-shaped. In one embodiment the teeth of the stator lamination plates are sufficiently wide relative to the area of stator slot openings so that the ratio of flux density in the tooth portion to flux density in the yoke portion is optimized for a given n pole operating configuration of the stator winding.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to dynamo-electric machines withlaminated rotors and stator cores, and more particularly to laminationconstructions in which stator teeth and rotor slots have relativedimensions such as to provide improved output for a given size machine.

2. Description of the Known Art

Arrangements are known for improving efficiency or power output ofdynamo-electric machines through the provision of certain slotdistributions in either a stator or rotor core element of the machine,e.g. U.S. Pat. No. 4,566,179 (Jan. 28, 1986), or by creating aprescribed variation of magnetic flux through a pole of the machinestator relative to the ampere-turns of the pole such as in U.S. Pat. No.4,209,720 (Jun. 24, 1980). There has not, however, been available amachine lamination construction by which the operating efficiency of adynamo-electric machine having a stacked laminated stator and/or rotoris improved by a prescribed ratio of inner diameter to outer diameterfor the lamination. Also, there has not been available a laminationconstruction by which the ratio of flux density in a tooth portion ofthe lamination to flux density in a yoke portion of the lamination canbe increased over that obtained conventionally, and, as a result, yieldgreater output or operating efficiency for the machine.

Rotors formed of a stack of laminations having closed slots equallyspaced from one another about the periphery of each lamination are knownfrom, for example, U.S. Pat. Nos. 2,794,138 (May 28, 1957) and 3,401,280(Sep. 10, 1968), both having been assigned to the assignee of thepresent invention.

Such rotors are ordinarily used in inductive AC motors, whereinconducting members which extend axially along the rotor through alignedslots of the stacked laminations interact with a rotating magnetic fieldcreated in an air gap between the outer circumference of the rotor andthe inner circumference of the machine stator. Windings embedded instator slots between radially inwardly projecting teeth of the stator,adjacent the air gap, are connected to the AC mains, and the statorwinding conductors pass through a certain order of the stator slots soas to cause magnetic flux in the air gap to rotate in synchronism withthe frequency of the AC mains.

Conventionally, each of the rotor slots is constricted between its topand bottom parts in the radial direction, to form a so-called neckportion of the slot. Such closed slot rotors ordinarily have the slotsin each of the rotor laminations formed with an inverted V shaped edgeat the upper boundary of the top part of the slot, with the center ofthe V creating a narrow bridge part between the upper boundary of theslot and the outer circumference of the lamination. Understandably, suchbridge part presents difficulties in machining of the closed slots atthe peripheries of the rotor laminations.

SUMMARY OF THE INVENTION

An object of the invention is to provide a dynamo-electric machineconstruction in which improvement is obtained through a greater amountof lamination material for both the stator core and the rotor of themachine, with less winding conductors than used previously.

Another object of the invention is to provide a dynamo-electric machinein which leakage flux from end turns of a winding embedded in slots of alaminated core, is substantially reduced.

A further object of the invention is to provide a dynamo-electricmachine which can achieve a greater horsepower to volume ratio than thatpreviously obtained.

Another object of the invention is to provide a closed slot rotorlamination which can be manufactured without imposing costly productionprocedures.

According to the invention, a dynamo-electric machine includes agenerally cylindrical casing and a stator core fixed in the casing andcomprised of stator plate laminations. A stator winding is embedded inslots extending from the bore of the stator core and a rotor issupported in the bore, the rotor comprising rotor plate laminations withconductor means for interacting with a magnetic field produced in an airgap between the outer periphery of the rotor and the inner periphery ofthe stator core.

Each of the stator plate laminations is comprised of a flat annularplate of ferro-magnetic material with a pre-selected outer diameter anda generally circular inner opening of a pre-selected inner diameter. Thestator plate lamination has a number of equally circumferentially spacedslots extending radially outwardly from the bore to an intermediatecircumference of the plate to establish teeth between the slots. A toothportion is defined by the teeth between the intermediate circumferenceand the bore, and a yoke portion is defined between the intermediatecircumference and the outer periphery of the stator lamination plate.

Each of the rotor plate laminations is comprised of a flat circularplate of ferro-magnetic material with a number of equallycircumferentially spaced closed slots extending radially near the outerperiphery of the plate. Each of the slots is defined by a semi-circularor curvilinear edge at an upper slot region adjacent to the outerperiphery of the plate and symmetrical about a radial center line. Endpoints of the curvilinear edge are coincident with ends of spacedsubstantially parallel sides of the slot, which sides extend equaldistances toward the center of the plate to define with the curvilinearedge a top part of the slot. The top part opens into a larger bottompart of the slot, which is substantially triangularly-shaped andsymmetrical about the radial center line.

For a given ratio of the pre-selected inner diameter to the pre-selectedouter diameter for the annular stator plate lamination, the stator teethare sufficiently wide relative to the area of the stator slot openingsso that the ratio of flux density in the tooth portion to flux densityin the yoke portion is optimized for a given n pole operatingconfiguration for the stator winding.

The various features of novelty which characterize the invention arepointed out with particularity in the claims annexed to and forming apart of the present disclosure. For a better understanding of theinvention, its operating advantages and specific objects attained by itsuse, reference should be had to the accompanying drawing and descriptivematter in which there is illustrated and described a preferredembodiment of the invention.

BRIEF DESCRIPTION OF THE DRAWING

In the drawing: p FIG. 1 is a side view, partly in section, of adynamo-electric machine in which the present invention may be embodied;

FIG. 2 is a front view of the machine in FIG. 1;

FIG. 3 is a plan view of a plate lamination for forming a stator core inthe machine of FIGS. 1 and 2;

FIG. 4 is an enlarged view of a part of the stator lamination in FIG. 3;

FIG. 5 is a plan view of another plate lamination for forming a rotor inthe machine of FIGS. 1 and 2;

FIG. 6 is an enlarged view of a part of the rotor lamination in FIG. 5;and

FIG. 7 is a table showing comparative data for physical relationshipsand ratios associated with the laminations of FIGS. 3 and 5 with theNEMA Standard 180 and 210 Frame sizes and 2-pole operations in relationto those of known laminations.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows a side view, in section, of a dynamo-electric machine 10 inwhich the present invention may be embodied. A front view of the machine10 is shown in FIG. 2.

Basically, the machine 10 includes a generally cylindrical outer casing12, and a generally cylindrical stator 14 fixed coaxially within theouter casing 12 and having a coaxial bore 16. A rotor 18 is supported bysuitable bearings 20a, 20b at the front and the back of casing 12, toextend axially within the bore 16 and for rotational movement about thebore axis. In the particular example shown, a shaft port 22 of the rotor18 extends axially from a front end shield 24 of the machine 10, and hasa key 26 projecting radially outward from a recess cut axially a certaindistance from the front of the shaft part 22. Key 26 serves to lock theshaft part 22 into a corresponding key way cut in a load member (notshown), e.g., a fan, to which rotational motive power is to be suppliedby the machine 10.

A back end shield 28 (FIG. 1) together with the casing 12 and the frontend shield 24 serve to contain and protect stator 14, rotor 18 andassociated conductive winding. In the example shown, a machine coolingfan 30 is mounted on a rotor stub part 32 which extends outside the backend shield 28, and directs an air current flow over the casing.

As shown in FIG. 1, the stator 14 is comprised of a stack of platelaminations 34 of ferromagnetic material. The lamination plates 34 arestacked face-to-face and are held together to form a core by any ofvarious means well known in the art. A number of slots extend along theaxial length of the stator 14, and project radially from the bore 16.These slots accommodate stator windings that have end turns 36, parts ofwhich are shown in FIG. 1. Details of individual plate laminationsembodying the invention in a preferred form are given below.

As shown in FIG. 1, the shaft part 22 of the rotor 18 extends axiallyfrom the machine casing or housing 12 and has a stack of rotorlaminations 40 fixed coaxially on the shaft part 22 intermediate thefront and back bearings 20a, 20b. Sets of conductive bars 42 passthrough a number of axially extending slots formed in the rotor 18 nearthe outer periphery of each of the laminations 40. The bars 42 areshorted to one another at the axial ends 44a, 44b of the rotorlamination stack by a set of end rings 46a, 46b.

In FIG. 1, the stator winding end turns 36 at axial end faces 48a, 48b,of the stator 14, are a source of stator flux leakage i.e. magnetic fluxproduced by the stator winding which does not interface with theconductive bars 42 in the rotor laminations 40. Inasmuch as stator fluxleakage does not contribute to the resultant torque exerted on the rotor18 when the stator winding or windings are energized, such flux leakageadversely affects the operating efficiency of the machine 10. It willtherefore be understood that any means by which potential sources ofstator flux leakage can be reduced or eliminated, are of greatimportance in dynamo-electric machine construction.

Certain machine construction standards are known in the industry,particularly those set out by ANSI/NEMA Standards Publication No.MG1-1987 (R1981). The entire contents of the cited publication areincorporated by reference herein.

The present invention aims to provide a dynamo-electric machineconstruction which conforms with industry standards, particularly withrespect to the so-called 180 and 210 frame size constructions. It willbe understood, however, that although dimensions for machine laminationsdisclosed herein will apply to the 180 and 210 frame sizes, theinvention can be embodied with advantage in machines of various sizesand proportions.

In FIG. 3, a stator plate lamination 34 for a 180 or 210 frame sizeaccording to the invention comprises a flat annular plate offerromagnetic material having an outer diameter "OD" according to thetabular value of FIG. 7, and a generally circular bore opening 50 of acertain inner diameter "ID". The lamination plate 34 has a number whichis 24 of equally circumferentially spaced slot openings 52 extendingradially from an intermediate circumference 54 to form the number ofteeth 56 which extend radially to the bore opening 50. In the embodimentof FIG. 3, the plate lamination 34 is a stator lamination so that thebore opening 50 defines one boundary for a stator-rotor air gap and abore for receiving the rotor. The width of each stator tooth 56 isdesignated at T₁.

The slot openings 52 are formed to contain one or more stator windingswhich extend axially through the stator 14 when like ones of thelamination plates 34 are stacked face-to-face with corresponding slotopenings 52 substantially aligned to communicate with one another. Inthe assembled machine 10 of FIGS. 1 and 2, the stator windings arearranged to correspond to an n (e.g. n=2, or 4, or 6, etc.) poleoperating configuration for the machine 10. When the stator windings areconnected to an outside electrical source, magnetic flux is producednext to the substantially aligned air gap peripheries or the stackedlamination plates 34 to interact with the conductive bars 42 of therotor 18.

The annular lamination plate 34 in FIG. 3 includes a tooth portion 58defined by the teeth 56 between the intermediate circumference 54 andthe air gap periphery. The remainder of the lamination plate 34 iscontinuous between the intermediate circumference 54 and the outerperiphery 59 to define a yoke portion 60 of the lamination plate 34.

FIG. 4 is an enlarged view of a part of the plate laminations 34 in FIG.3. Specifically, a single slot opening 52 is shown surrounded byadjacent teeth 56. Lip parts 61 project circumferentially toward oneanother from the adjacent teeth 56, to define a mouth 62 of width W₁₀ ofthe slot opening 52. As is known, mouth 62 should be sufficiently wideto allow individual conductors 64 forming the stator winding to beinserted in the opening 52 through the mouth 62 when the machine 10 isassembled. The lip parts 61 act to seat a winding closure wedge 66 whichholds the conductors 64 of the stator winding firmly in place within thestator slots formed by the openings 51. To separate individual statorwindings, an insulating winding separator 68 may be positioned as shownin FIG. 4 in the stator slots, and an insulating film 70 positionedagainst the walls of the stator slots prevents arcing or shortcircuiting of individual conductors 64 with the material of which thelaminations 34 are made.

According to one aspect of the invention, for a given ratio of innerdiameter ID to outer diameter OD of the plate 34, the teeth 56 aresufficiently wide relative to the area of the slot openings 52 so thatthe ratio of flux density in the tooth portion 58 (FIG. 3) (BT₁) to fluxdensity in the yoke portion 60 (BY₁) when the stator windings areenergized, is substantially optimized for a given n pole operation ofthe stator windings. The actual number of slot openings is not critical.For example, the lamination plate 34 in FIG. 3 is shown with 24 slotsand has the dimensions in FIG. 7 suitable for incorporation in a 180 or210 frame size machine.

An underlying concept of the present invention is to utilize maximumamounts of ferromagnetic material (e.g., iron) for the lamination plates34 and minimum amounts of winding conductors, e.g., the individualconductors 64 in a dynamo-electric machine having a desired powerhandling capability.

In the disclosed embodiment, the ratios of the tooth portions 58 to yokeportions 60 for the lamination plates 34 substantially differ from knownconstructions, as does the ratio of inner diameter to outer diameter ofthe lamination plates 34. The lip parts 61 thus become very smallrelative to the known structures as a consequence of the relative wideteeth 56. Use of less winding material also results in smaller end turns(e.g., the stator end turns 36) at the end faces to the statorlamination stack, and, thus, undesired flux leakage is significantlyreduced from that in the prior constructions.

FIG. 5 is a plan view of a rotor lamination for a 180 or 210 frame size,according to the present invention. The rotor lamination is formed of aflat circular plate 70 of ferromagnetic material. The plate 70 has anumber (e.g., 28 for n=2) of uniformly circumferentially spaced closedslots 72 extending symmetrically about radial center lines near theouter periphery of the plate 70. Rotor teeth formed between slots 72have each a width T₂. Slots 72 are formed to contain conductive bars 42(FIG. 1) which extend substantially parallel to the axis of the rotor 18when the plates 70 are stacked face-to-face with the corresponding slots72 substantially aligned to communicate with one another. Each of theslots 72 is substantially rectangular through an upper slot region 74,as shown in FIGS. 5 and 6. A curvilinear or semi-circular edge 76 ofeach slot 72, adjacent the outer circumference 78 of the plate, issymmetrical about the radial center line of the slot 72. The curvilinearedge has a semi-circular shape with a radius of between 0.625 mm. and0.750 mm. End points 80a, 80b, of the semi-circular edge 76 arecoincident with ends of spaced substantially parallel edges 82a, 82b ofthe plate 70. The edges 82a, 82b extend equal distances L₁ in thedirection towards the center C of the rotor lamination plate 70. Abridge area 84 of the plate 70 is thus formed between the edge 76 andthe outer circumference 78.

As seen in FIGS. 5 and 6, a top part of each slot 72 is defined by theedge 76 and the parallel edges 82a, 82b, opens into a bottom part of theslot which is substantially triangularly shaped and symmetrical aboutthe radial center line. From a base line B, opposite ends of the edges82a, 82b are curved continuously at a first radius R₁ to diverge outwardfrom the center line over an arc of approximately 90 degrees, and thencurve toward the center C of the plate 70 at a second radius R₂ overanother approximately 90 degrees arc, as shown in FIG. 6, to a set ofpoints 84a, 84b. From the latter set of points, spaced straight edges86a, 86b of the plate 70 converge toward one another over a radiallymeasured length L₂ toward the plate center C and terminate at points88a, 88b. Another curvilinear or semicircular edge 90 joins the points88a, 88b.

Reference is made hereto to "punched diameter" and "diameter" in thecontext of both stator and rotor laminations plates. In this context,"punched diameter" means "as punched" by a punch press and does notcontemplate finishing operations for establishing air gap definingfinished surfaces. For example, a rotor lamination plate diameter ofabout "102 mm." would be inclusive of a lamination plate having anominal, as punched, diameter of 102 mm., as well as a rotor laminationstacked within a finished rotor and having a finished outer diametersomewhat less than 102 mm. so that a proper air gap will be maintainedbetween the rotor and stator core of the machine 10.

Table 1, below, shows preferred values of dimensions for both the statorlamination plate 34 and the rotor lamination plate 70 for a 2-pole,3-phase dynamo-electric machine 10 constructed according to the NEMAStandard 180 frame.

In the following tables S₁ is a number of stator slots; S₂ is a numberof rotor slots, T₁ is a stator tooth width and T₂ is a rotor toothwidth.

                  TABLE 1                                                         ______________________________________                                        NEMA STANDARD 180 FRAME                                                       ______________________________________                                        STATOR LAMINATION PLATE 34:                                                   Punched Outer Diameter  203     mm.                                           Punched Inner Diameter  102     mm.                                           Number of Slots 52 (S.sub.1)                                                                          24                                                    Tooth Width T.sub.1     7.250   mm                                            Slot Width 62 (W.sub.10)                                                                              2.600   mm.                                           ROTOR LAMINATION PLATE 70:                                                    Punched Outer Diameter  102     mm                                            Punched Inner Diameter  34.468  mm                                            Number of Slots 72 (S.sub.2)                                                                          28                                                    Radius of Edge 76       0.625   mm                                            Length L.sub.1          6.113   mm                                            Radii R.sub.1 and R.sub.2                                                                             0.762   mm                                            Length L.sub.2          11.644  mm                                            Radius of edge 90       0.762   mm                                            ______________________________________                                    

Table 2, below, gives preferred values for the plates 34, 70 in a2-pole, 3-phase NEMA Standard 210 frame.

                  TABLE 2                                                         ______________________________________                                        NEMA STANDARD 210 FRAME                                                       ______________________________________                                        STATOR LAMINATION PLATE 34:                                                   Punched Outer Diameter  242     mm.                                           Punched Inner Diameter  122     mm.                                           Number of Slots 52 (S.sub.1)                                                                          24                                                    Tooth Width T.sub.1     8.500   mm.                                           Slot Width 62 (W.sub.10)                                                                              3.200   mm.                                           ROTOR LAMINATION PLATE 70:                                                    Punched Outer Diameter  122     mm.                                           Punched Inner Diameter  42.836  mm                                            Number of Slots 72 (S.sub.2)                                                                          28                                                    Radius of Edge 76       0.750   mm.                                           Length L.sub.1          6.488   mm.                                           Radii R.sub.1 and R.sub.2                                                                             0.762   mm.                                           Length L.sub.2          16.936  mm.                                           Radius of edge 90       0.762   mm.                                           ______________________________________                                    

FIG. 7 is a table in which physical constants, relationships, and ratiosassociated with the laminations dimensioned according to the inventionin Tables 1 and 2, are compared with the closest known priorconfigurations, for 2 pole AC induction motors with NEMA 180 and 210sizes. For comparison with known values, the specific measurements havebeen converted into inches. Included in FIG. 7 is a value of the net andgross area of the slots in the stator multiplied by the number (S₁) ofslots in the stator. The net slot area (ASLOT-NET) equals the gross slotarea (ASLOT-GROSS, see FIG. 3) less the area occupied by the slotliners, separators, and wedges and less the area at the mouth notavailable for insertion of windings (see FIG. 4).

It will be seen from FIG. 7 that in addition to having a lower innerdiameter to outer diameter ratio than in the prior correspondinglaminations, the teeth width of the present laminations is generallygreater than in prior laminations. The product of the number of rotorslots (S₂) times the rotor tooth width (T₂), divided by the product ofthe number of stator slots (S₁) times the stator toooth width (T₁) is,for the 180 and 210 sizes, preferably in the range of 0.825 to 0.90. Inthe examples of FIG. 7, the ratio in both cases is 0.850.

FIG. 7 provides specific values for various ratios which are used todefine the improved lamination. The ratio ID/OD represents the ratio ofthe inner diameter of the stator lamination to the outer diameter andgives an indication of the larger amount of ferromagnetic material thancopper which is used in the present laminations. The ratio Tl/Tsrepresents a ratio of tooth width (T₁) of the stator lamination to thebore circumference divided by the number of stator slots S₁,TS=π×ID/S₁). This effectively provides an indication of the tooth width.The value Btl/Byl can be used to represent the flux density in the toothto the flux density in the yoke if it is assumed that the flux in thetooth and yoke is the same, which is a close approximation. This ratiogives an indication of tooth to yoke ratio. This ratio is alsodeterminable geometrically from a stator lamination by the relatioshipBtl/Byl×(π×n×Y1)/(S₁ ×T₁) where n is the number of poles, Y1 is thedimension shown in FIG. 3 and S₁ and T₁ are as defined above.

In order to compare specific ratios of the prior art laminationcross-sections with those of the present invention see the table belowidentical to FIG. 7.

    __________________________________________________________________________    LAMINATION CROSS SECTIONS                                                                        180 FRAME   210 FRAME                                                         2 POLE      2 POLE                                                            PRIOR                                                                             PRESENT PRIOR                                                                             PRESENT                                                       ART INVENTION                                                                             ART INVENTION                                  __________________________________________________________________________    OD (in)            7.478                                                                             7.992   8.775                                                                             9.528                                      ID/OD              .535                                                                              .5025   .556                                                                              .504                                       T.sub.1 /T.sub.S   .450                                                                              .543    .404                                                                              .532                                       BT.sub.1 /BY.sub.1 1.144                                                                             1.101   1.142                                                                             1.100                                      S.sub.2 T.sub.2 /S.sub.1 T.sub.1                                                                 .808                                                                              .850    .903                                                                              .850                                       W.sub.10 (in)      .100                                                                              .102    .125                                                                              .126                                       S.sub.1 (NUMBER OF STATOR SLOTS)                                                                 36  24      36  24                                         (S.sub.1) × (A SLOT-GROSS) (in.sup.2)                                                      5.86                                                                              5.77    8.39                                                                              8.60                                       (S.sub.1) × (A SLOT-NET) (in.sup.2)                                                        4.77                                                                              4.95    6.56                                                                              7.50                                       S.sub.2 (NUMBER OF ROTOR SLOTS)                                                                  28  28      26  28                                         __________________________________________________________________________

It should be remembered that the resulting improved laminations are theresult of an interaction of the various values. Thus, not each and everyone of the values is consistently changed for each embodiment. Theresult, however, is consonant with the underlying concept of the presentinvention which, as mentioned, is to utilize maximum amount oflamination material and minimum amount of winding (i.e., copper)material.

Machines employing laminations configured according to the inventionhave yielded greater horsepower to volume ratios when compared withknown corresponding machines. Of course, variations occur depending onefficiency. Table 3 below shows a comparison between percent efficiencyand electromagnetic volume for 2 pole AC induction motors withlaminations according to the present invention, and corresponding motorsaccording to the prior art.

                  TABLE 3                                                         ______________________________________                                                % EFFICIENCY VOLUME (OD).sup.2 L*                                     HP        PRIOR     NEW      PRIOR   NEW                                      ______________________________________                                        2-POLE AC INDUCTION MOTORS - 180 FRAME                                        5 (LO EFF)                                                                              87.2      86.9     2.75    2.27                                     5 (HI EFF)                                                                              90.1      90.4     3.67    3.30                                     7.5 (LO EFF)                                                                            87.5      87.7     3.21    2.68                                     7.5 (HI EFF)                                                                            90.7      90.9     4.12    3.70                                     2-POLE AC INDUCTION MOTORS 210 FRAME                                          10 (LO EFF)                                                                             90.2      91.1     5.05    4.68                                     10 (HI EFF)                                                                             91.5      93.3     5.99    7.61                                     15 (LO EFF)                                                                             90.7      91.4     5.99    5.27                                     15 (HI EFF)                                                                             92.0      92.4     5.99    7.03                                     ______________________________________                                         *mm.sup.3 × 10.sup.4 Thus, tabular value 2.75 means 2.75 (10.sup.4)     mm.sup.3 ; tabular value 2.27 means 2.27 (10.sup.4) mm.sup.3 ; etc.      

Through the use of relatively wider teeth in the present laminations,flux density saturation for a given size and power machine can beachieved with a shorter lamination stack than in the priorconstructions. Hence, the electromagnetic volume (OD)² L for machinesaccording to the invention is generally lower than the volumes in theprior machines for about the same or even better efficiency. In the 10HP hi efficiency motor a greater volume was used, but a rathersubstantial improvement in efficiency was achieved. For the hiefficiency 15 HP motor a cheaper steel was used which had greater lossesso that even though there was a greater volume and only slightefficiency improvement, the cost saving was significant and could onlybe achieved using the present design. The use of wider or fatter teethalso produces a relatively higher flux density in the air gap betweenstator and rotor lamination stacks in machines according to theinvention. Thus, more torque is produced from the rotor for a givenmachine size.

Terminology used herein such as "generally cylindrical", "essentiallyround", and "annular", with reference to or in connection withlaminations (or plates) or structures made from such laminations (e.g."cores", stators, etc.), is inclusively descriptive of laminations,cores, etc, that do not have "true round" configurations due to thepresence of peripherally located "key slots", marker notches, flatsresulting from production processes (such as occur from zig-zag punchlines, for example), and so forth.

While the foregoing description represents preferred embodiments of theinvention, it will be obvious to those skilled in the art that variouschanges and modifications may be made, without departing from the spiritand scope of the present invention.

I claim:
 1. A dynamo-electric machine comprising:a generally cylindricalcasing; a stator core fixed in said casing and comprised of statorlamination plates of ferromagnetic material, said stator core having acylindrical bore; a stator winding embedded in stator slots radiallyprojecting from the bore and which slots extend generally axially alongthe core, with end turns of said winding extending beyond end faces ofsaid stator core; a rotor supported in said bore for rotational movementand comprised of rotor lamination plates of ferromagnetic material, saidrotor including conductive means for interacting with a magnetic fieldproduced in an air gap between an outer periphery of said rotor and aninner periphery of the stator core when said stator winding isenergized; wherein each of said stator lamination plates comprises: aflat annular plate of ferromagnetic material having a preselected outerdiameter and a generally circular inner opening of a preselected innerdiameter which forms .[.the stator.]. .Iadd.said .Iaddend.bore when.[.like ones of.]. said plates are stacked face-to-face with oneanother, said plate having a number of uniformly circumferentiallyspaced slots which project radially outwardly from the bore to anintermediate circumference of said plate to define teeth between theslots, said slots forming said stator slots when corresponding slotopenings in the .[.like.]. plates are substantially aligned tocommunicate with one another and the plates are stacked, said annularplate including a tooth portion defined by said teeth between saidintermediate circumference and said circular inner opening, and a yokeportion defined between said intermediate circumference and an outerperiphery of said plate, and wherein each of said rotor laminationplates comprises a flat circular plate of ferromagnetic material havinga number of equally circumferentially spaced closed .Iadd.rotor.Iaddend.slots extending radially in a region near the outer peripheryof said plate, said .Iadd.rotor .Iaddend.slots being formed to containconducting members which extend axially along the rotor when .[.likeones of.]. said .Iadd.rotor lamination .Iaddend.plates are stackedface-to-face with corresponding slots in communication with one another;and wherein for a given ratio of said preselected inner diameter to saidpreselected outer diameter for said annular plate of each of said statorlamination plates, said teeth are sufficiently wide relative to.[.the.]. .Iadd.an .Iaddend.area of said .[.slot openings.]. .Iadd.slots.Iaddend.so that the ratio of flux density in said tooth portion to fluxdensity in said yoke portion in response to energization of the statorwinding is optimized for the number of poles n in the operatingconfiguration of said stator winding; and wherein the ratio of innerdiameter to outer diameter of the annular plate forming said statorlamination plate is in the range of about 0.5025 to 0.504 for n equals2.
 2. The dynamo-electric machine of claim 1, wherein each of the rotorslots is defined by a curvilinear edge at an upper slot region adjacentthe periphery of said rotor lamination plate and symmetrical about aradial center line, end points of the curvilinear edge being coincidentwith ends of spaced substantially parallel sides of the upper slotregion, which sides extend equal distances in .[.the.]. .Iadd.a.Iaddend.direction toward .[.the.]. .Iadd.a .Iaddend.center of each ofsaid rotor lamination plates to define with the curvilinear edge a toppart of the slot, said top part opening into a bottom part of the slotwhich is substantially triangularly-shaped and symmetrical about theradial center line.
 3. The dynamo-electric machine of claim 1, whereinsaid stator winding is comprised of a minimum number of conductorscontained in the stator slots for said operating configuration, so thatflux leakage from said end turns at the end faces of said stator issubstantially reduced.
 4. The dynamo-electric machine of claim 1,wherein said ratio of flux density is from about 1.10 .Iadd.to1.14.Iaddend..
 5. The dynamo-electric machine of claim, 1, wherein theouter diameter of said stator lamination plate is about 203 mm.
 6. Thedynamo-electric machine of claim, 1, wherein the outer diameter of saidstator lamination plate is about 3 mm.
 7. The dynamo-electric machine ofclaim 2 wherein said spaced substantially parallel sides of the upperslot region of each rotor slot extend a distance in the range from about6.113 mm. to 6.488 mm. and said bottom part of each rotor slot extends adistance in the range from about 11.644 mm to 16.936 mm.
 8. Adynamo-electric machine, comprising:a rotor made from rotor laminationplates having a preselected number of slots of predetermined size; astator core made of stator lamination plates wherein the stator core iswound to provide for an operating configuration with a number of polesduring stator winding energization, and wherein each stator laminationplate comprises: a flat annular plate of ferromagnetic material having agiven outer diameter and a generally circular bore opening of a certaininner diameter, each said annular plate having a number of uniformlycircumferentially spaced slot openings extending radially from anintermediate circumference of said plate to form a number of teeth whichextend radially to an air gap periphery of said plate, wherein said slotopenings are formed to contain electrically conducting elements whichextend axially through .[.the.]. .Iadd.a .Iaddend.lamination stack when.[.like ones of the.]. .Iadd.flat .Iaddend.annular plates are stackedface-to-face with corresponding slot openings in communication with.Iadd.one .Iaddend.another, said conducting elements being arranged tocorrespond to .[.said.]. .Iadd.an .Iaddend.n pole operatingconfiguration, .Iadd.wherein n is a number of poles in a given n-poleoperating configuration, .Iaddend.and magnetic flux is produced aroundthe conducting elements when electric current energizes the conductingelements, said annular plate including a tooth portion defined by saidteeth between said intermediate circumference and said circular boreopening, and a yoke portion defined by a substantially continuoussurface of said plate between said intermediate circumference and anouter periphery of said plate radially opposite said bore opening, andwherein each of said rotor lamination plates comprises: a flat circularplate of ferromagnetic material having .[.a.]. .Iadd.said preselected.Iaddend.number of .Iadd.slots, said slots being .Iaddend.equallycircumferentially spaced closed slots extending radially in a regionnear .[.the.]. .Iadd.an .Iaddend.outer periphery of said plate,.Iadd.and rotor teeth formed between said slots, each rotor tooth havinga predetermined width, .Iaddend. said slots being formed to containconducting members which extend substantially axially along the rotorwhen .[.like ones of.]. said .Iadd.rotor lamination .Iaddend.plates arestacked face-to-face with corresponding slots in communication with oneanother, and wherein .[.the.]. .Iadd.a .Iaddend.product of the number ofsaid slots of each of said rotor lamination plates times .[.the.]..Iadd.said predetermined .Iaddend.width of .[.a.]. .Iadd.the.Iaddend.rotor tooth is a first value, .[.the.]. .Iadd.a.Iaddend.product of .[.the.]. .Iadd.a .Iaddend.number of .[.statorslots.]. .Iadd.slot openings .Iaddend.times the width of the statorteeth is a second value, and the ratio of the first value to the secondvalue is .Iadd.in .Iaddend.the range of 0.825 to 0.90.
 9. Thedynamo-electric machine of claim 8, wherein each of said slots of eachof said rotor lamination plates is defined by a curvilinear edge at anupper slot region adjacent the periphery of the circular plates andsymmetrical about a radial center line, end points of the curvilinearedge being coincident with ends of spaced substantially parallel sidesof the upper slot region, which sides extend equal distances .[.innthe.]. .Iadd.in a .Iaddend.direction toward .[.th.]. .Iadd.a.Iaddend.center of said circular plate to define with the curvilinearedge a top part of the slot, said top part opening into a bottom part ofthe slot which is substantially triangular-shaped and symmetrical aboutthe radial center line.
 10. The dynamo-electric machine of claim 9,wherein said curvilinear edge of each closed slot in said rotorlamination plates is semi-circular with a radius in the range from about0.625 mm. to 0.750 mm.
 11. The dynamo-electric machine of claim 9,.[.where.]. .Iadd.wherein .Iaddend.said curvilinear edge of each closedslot in said rotor lamination plates is semi-curvilinear with a radiusin the range of from about 0.625 mm. to 0.750 mm.
 12. Thedynamo-electric machine of claim 9, wherein said spaced substantiallyparallel sides of the upper slot region of each rotor slot extend adistance in the range from about 6.113 mm. to 6.488 mm. and said bottompart of each rotor slot extends a distance in the range from about11.644 mm. to 16.936 mm. .Iadd.13. A dynamo-electric machinecomprising:a generally cylindrical casing; a stator core fixed in saidcasing and comprised of stator lamination plates of ferromagneticmaterial, said stator core having a cylindrical bore; a stator windingembedded in stator slots radially projecting from the bore and whichslots extend generally axially along the core, with end turns of saidwinding extending beyond end faces of said stator core; a rotorsupported in said bore for rotational movement and comprised of rotorlamination plates of ferromagnetic material, said rotor includingconductive means for interacting with a magnetic field produced in anair gap between an outer periphery of said rotor and an inner peripheryof the stator core when said stator winding is energized; wherein eachof said stator lamination plates comprises: a flat annular plate offerromagnetic material having a preselected outer diameter and agenerally circular inner opening of a preselected inner diameter whichforms said bore when said stator lamination plates are stackedface-to-face with one another, said plate having a number of uniformlycircumferentially spaced slots which project radially outwardly from thebore to an intermediate circumference of said plate to define teethbetween the slots, said slots forming said stator slots whencorresponding slot openings in the plates are substantially aligned tocommunicate with one another and the plates are stacked, said annularplate including a tooth portion defined by said teeth between saidintermediate circumference and said circular inner opening, and a yokeportion defined between said intermediate circumference and an outerperiphery of said plate, and wherein each of said rotor laminationplates comprises a flat circular plate of ferromagnetic material havinga number of equally circumferentially spaced closed slots extendingradially in a region near the outer periphery of said plate, said slotsbeing formed to contain conducting members which extend axially alongthe rotor when said plates are stacked face-to-face with correspondingslots in communication with one another; and wherein for a given ratioof said preselected inner diameter to said preselected outer diameterfor said annular plate of each of said stator lamination plates, saidteeth are sufficiently wide relative to an area of said slot openings sothat the ratio of flux density in said tooth portion to flux density insaid yoke portion in response to energization of the stator winding isoptimized for a number of poles n in a given n-pole operatingconfiguration of said stator winding; and wherein the ratio of innerdiameter to outer diameter of the annular plate forming said statorlamination plate is in the range of about 0.5025 to 0.504 for n equals 2wherein n is the number of poles in the operating configuration of saidstator winding; wherein each of the rotor slots is defined by acurvilinear edge at an upper slot region adjacent the periphery of saidrotor lamination plate and symmetrical about a radial center line, endpoints of the curvilinear edge being coincident with ends of spacedsubstantially parallel sides of the upper slot region, which sidesextend equal distances in a direction toward a center of each of saidrotor lamination plates to define with the curvilinear edge a top partof the slot which is substantially triangularly-shaped and symmetricalabout the radial center line. .Iaddend. .Iadd.14. A dynamo-electricmachine comprising:a generally cylindrical casing; a stator core fixedin said casing and comprised of stator lamination plates offerromagnetic material, said stator core having a cylindrical bore; astator winding embedded in stator slots radially projecting from thebore and which slots extend generally axially along the core, with endturns of said winding extending beyond end faces of said stator core; arotor supported in said bore for rotational movement and comprised ofrotor lamination plates of ferromagnetic material, said rotor includingconductive means for interacting with a magnetic field produced in anair gap between an outer periphery of said rotor and an inner peripheryof the stator core when said stator winding is energized; wherein eachof said stator lamination plates comprises: a flat annular plate offerromagnetic material having a preselected outer diameter and agenerally circular inner opening of a preselected inner diameter whichforms said bore when said stator lamination plates are stackedface-to-face with one another, said plate having a number of uniformlycircumferentially spaced slots which project radially outwardly from thebore to an intermediate circumference of said plate to define teethbetween the slots, said slots forming said stator slots whencorresponding slot openings in the plates are substantially aligned tocommunicate with one another and the plates are stacked, said annularplate including a tooth portion defined by said teeth between saidintermediate circumference and said circular inner opening, and a yokeportion defined between said intermediate circumference and an outerperiphery of said plate, and wherein each of said rotor laminationplates comprises a flat circular plate of ferromagnetic material havinga number of equally circumferentially spaced closed rotor slotsextending radially in a region near the outer periphery of said plate,said slots being formed to contain conducting members which extendaxially along the rotor when said plates are stacked face-to-face withcorresponding slots in communication with one another; and wherein for agiven ratio of said preselected inner diameter to said preselected outerdiameter for said annular plate of each of said stator laminationplates, said teeth are sufficiently wide relative to an area of saidslot openings so that the ratio of flux density in said tooth portion toflux density in said yoke portion in response to energization of thestator winding is optimized for a number of poles n in a given n-poleoperating configuration of said stator winding; and wherein said ratioof flux density is from about 1.10 to 1.14. .Iaddend. .Iadd.15. Adynamo-electric machine comprising:a generally cylindrical casing; astator core fixed in said casing and comprised of stator laminationplates of ferromagnetic material, said stator core having a cylindricalbore; a stator winding embedded in stator slots radially projecting fromthe bore and which slots extend generally axially along the core, withend turns of said winding extending beyond end faces of said statorcore; a rotor supported in said bore for rotational movement andcomprised of rotor lamination plates of ferromagnetic material, saidrotor including conductive means for interacting with a magnetic fieldproduced in an air gap between an outer periphery of said rotor and aninner periphery of the stator core when said stator winding isenergized; wherein each of said stator lamination plates comprises: aflat annular plate of ferromagnetic material having a preselected outerdiameter and a generally circular inner opening of a preselected innerdiameter which forms said bore when said stator lamination plates arestacked face-to-face with one another, said flat annular plate having anumber of uniformly circumferentially spaced slots which projectradially outwardly from the bore to an intermediate circumference ofsaid plate to define teeth between the slots, said slots forming saidstator slots when corresponding slot openings in the stator laminationplates are substantially aligned to communicate with one another and theplates are stacked, said annular plate including a tooth portion definedby said teeth between said intermediate circumference and said circularinner opening, and a yoke portion defined between said intermediatecircumference and an outer periphery of said plate, and wherein each ofsaid rotor lamination plates comprises a flat circular plate offerromagnetic material having a number of equally circumferentiallyspaced closed rotor slots extending radially in a region near an outerperiphery of said plate, said rotor slots being formed to containconducting members which extend axially along the rotor when said rotorlamination plates are stacked face-to-face with corresponding slots incommunication with one another; and wherein for a given ratio of saidpreselected inner diameter to said preselected outer diameter for saidannular plate of each of said stator lamination plates, said teeth aresufficiently wide relative to an area of said slot openings so that theratio of flux density in said tooth portion to flux density in said yokeportion in response to energization of the stator winding is optimizedfor a number of poles n in an operating configuration of said statorwinding; and wherein said stator winding is comprised of a minimumnumber of conductors contained in the stator slots for said operatingconfiguration, so that flux leakage from said end turns at the end facesof said stator is substantially reduced. .Iaddend. .Iadd.16. Adynamo-electric machine comprising:a rotor comprising a plurality ofrotor plates each having a preselected number of closed slots ofpredetermined size for containing conducting means, each slot beingequally circumferentially spaced and extending radially near an outerperiphery of each plate, each rotor plate having teeth formed by saidslots, each rotor tooth having a predetermined width; and a stator corewound for energization, the stator core comprising a plurality of statorplates having a predetermined outer diameter, each stator plate having anumber of uniformly circumferentially spaced slot openings forcontaining electrically conducting means, each slot opening extendingradially from an intermediate circumference of the stator plate to forma number of stator teeth, each stator tooth having a preselected width,said stator teeth extending radially to an air gap periphery of thestator plate, each stator plate having a bore opening and a toothportion defined by the teeth between the intermediate circumference andthe bore opening and a yoke portion defined by a substantiallycontinuous surface of the stator plate between the intermediatecircumference and an outer periphery of the stator plate radiallyopposite the bore opening, wherein a product of a number of slots ofeach rotor plate times said predetermined width of the rotor toothequals a first value and a product of a number of the slot openingstimes said preselected width of the stator tooth equals a second value,the ratio of the first value to the second value being fromapproximately 0.825 to approximately 0.900. .Iaddend.